A patient smashes their head against the steering wheel in a car accident. This most commonly results in damage to the frontal and temporal lobes as their brain bangs against the inside of the skull. What sensory modality is most likely to be damaged as a result?
- The olfactory bulbs and nerve lie underneath the frontal lobe and are often damaged in acceleration/deceleration injuries. Taste is also secondarily affected as there is a huge component of smell to taste.
- Olfaction is the only sensory modality which bypasses the thalamus.
A patient presents with marked ptosis of the left eye. When you open the eye, you see that the pupil is dilated and the eye is deviated downward and outward. The pathology localizes to...
The oculomotor nerve
- Controls all muscles except lateral rectus + superior oblique
- Damage = "down and out"
- Controls levator palpebrae superioris
- Damage = ptosis
- Contains parasympathetic fibers
- Damage = dilated pupil
- Found in Edinger-Westphal nucleus in brainstem
- In periphery of occulomotor nerve
- Compressive lesion = dilated pupil
- Microvascular disease (DM) = extraocular weakness
You order an MRA on a patient with a 3rd nerve palsy because you know there could be an aneurysm of the...
Ipsilateral posterior communicating artery
- CN III emerges from brainstem between posterior cerebral artery + superior cerebellar artery and runs under the posterior communicating artery
- Aneurysm of posterior communicating artery can cause CN palsy or dilated pupil
A patient presents with double vision. She says that she was hit in the eye with a softball several months prior. As she sits in the waiting room, you notice the following head posture. You immediately know that the pathology localizes to...
The trochlear nerve
- Controls superior oblique muscle, which depresses and intorts the eye
- The only CN that decussates (L nerve innervates R muscle)
- The only CN that exits from the dorsal aspect of the brainstem
- When damaged, causes vertical diplopia + patients compensate by tilting the head towards the shoulder of unaffected side
A 45 year-old man develops complete inability to move his left eye as well as a fixed, dilated pupil and ptosis. He is numb on the upper and middle part of his face as well. This is due to a lesion of the...
- Cavernous sinus is venous plexus lateral to sella turcica, bordered by temporal + sphenoid bones
- CN III, CN IV, CN VI
- Ophthalmic nerve (V1), maxillary nerve (V2)
- Internal carotid artery
- Damage causes complete unilateral ophthalmoplegia + numbness in distribution of ophthalmic + maxillary nerve
- Cavernous sinus syndrome = emergency
- In diabetics, caused by mucormycosis
- Tolosa-Hunt syndrome = idiopathic granulomatous disease of cavernous sinus
A patient presented with paralysis of upgaze due to compression of the vertical gaze center in midbrain, circled in red. What is the source of the primary tumor?
- Pineal gland is midline endocrine gland that secretes melatonin
- Melatonin helps regulate sleep/wake cycle
- Pineal gland stimulated in dark, inhibited in light
- Pineal gland is usually calcified
Pinealomas are asymptomatic until they affect the midbrain and cause visual symptoms
- Primary upgaze
- Germinomas are most common pineal-region tumors
A patient has a stroke affecting their left frontal lobe. Is this case, their eyes will deviate to the...
A patient has a seizure focus originating in their left frontal lobe. Is this case, their eyes will deviate to the...
Left in stroke, right in seizure
Frontal eye fields are cortical areas that control eye movement
- Each frontal eye field deviates the eyes to the opposite side
- Abnormalities of frontal eye fields produce gaze preference
In stroke, eye deviates towards the lesion
In seizure, eye deviates away from lesion
The patient shown below most likely suffers from a lesion of the...
Superior cervical ganglion
- Ptosis, miosis, anhydrosis
- Due to lesion anywhere in sympathetic pathway
- Common in carotid artery dissections as the sympathetic fibers run along the carotid artery
- Common in vertebral artery dissections as part of the Wallenberg syndrome
- Injury to lateral part of medulla
- Contralateral pain + temperature deficit of trunk and upper extremity
- Ipsilateral pain + temperature deficit of face
A 35 year-old man, when looking to the right, cannot adduct his left eye and there is abducting nystagmus of his right eye, convergence is preserved. This is known as an internuclear opthalmoplegia and is due to a lesion of the medial longitudinal fasciculus, which connects the 3rd and 6th cranial nerves. In what condition is this most commonly seen?
Medial longitudinal fasciculus (MLF) links CN III on one side with CN VI on other side
- This ensures simultaneous activation of medial and lateral rectus msucles to preserve conjugate gaze
A 24 year-old female wakes up with blurry vision and pain with eye movement. You diagnosis her with optic neuritis and in order to help her recover more rapidly, suggest treatment with...
Most subtle abnormality of patient with optic neuritis is loss of color vision (color red in particular)
Giving IV steroids to patient with optic neuritis hastens clinical recovery and may delay occurrence of second demyelinating episode, but does not have long-term impact
- 3 days of steroids followed by oral taper
Severe relapse can be treated with plasmapheresis
A patient would like to know her risk for developing multiple sclerosis. You tell her this is most closely correlated with...
The number of lesions on brain MRI
Classic MRI in MS:
- Ovoid, periventricular white matter lesions = Dawson's fingers
- Active lesions show enhancement, often with incomplete ring
Old lesions are hypointense on T1 = black holes
- Irreversible axonal damage
- Brain atrophy
- Spinal cord lesions can enhance with contrast
- EBV, low vitamin D, genetics, females, age ~30, live far from equator
Favorable prognostic factors:
- White, female, young, sensory symptoms at onset, full recovery from initial attack, fewer relapses, fewer lesions on baseline MRI
Signs and symptoms:
- Optic neuritis, sensory disturbance, pain, weakness, diplopia, ataxia, bowel/bladder dysfunction, depression
- L-Hermitte's sign = electrical shock sensations in limbs and body brought on by movement of the neck (cervical spinal cord pathology)
- Uhthoff's phenomena = heat exposure worsens MS symptoms
- McDonald criteria: 2 attacks + MRI or oligoclonal bands in CSF
- Starts relapsing-remitting
- Then secondary progressive after several decades
- 10% have primary progressive (gradual increase w/o attacks)
Natalizumab (Tysabri) = monthly infusion
- Monoclonal antibody that prevents T-cells from crossing BBB
- Has been associated with PML
Fingolimod (Gilyena) = oral med
- Blocks T-cell egress from lymph nodes
- SE: bradycardia, infection, macular edema
Teriflunimode (Aubagio) = oral med
- SE: GI upset, reversible alopecia
- CI in pregnancy (category X)
- Dimethyl fumarate (Tecfidera) = oral med
- Approved for secondary progressive form
- No treatment for primary progressive
A 45 year-old woman presents with weakness of her legs, and sensory loss below her chest. Several years prior, she had optic neuritis of both eyes and an MRI of her brain at the time showed hyperintensity of the optic nerves and chiasm. An spinal MRI, below, shows a lesion of the spinal cord extending over several spinal segments. You suspect she suffers from...
Neuromyelitis optica (NMO)/Devic's disease
A demyelinating disease characterized by:
- Optic neuritis (bilateral)
- Transverse myelitis + MRI showing contiguous spinal cord lesion 3+ segments in length
- brain MRI non-diagnostic of MS
- Antibody directed against astrocytes on BBB
- More severe than MS
- F > M
- Oral immunosupression
- Treatment for MS WORSENS disease
A not uncharacteristic finding of patients with NMO is intractable hiccups and nausea/vomiting. This is due to a lesion of the...
- A small protuberance found at the inferoposterior limit of the fourth ventricle
- A medullary structure in the brain that controls vomiting
- A patient has the MRI below. If the patient presented with visual complaints, what did they most likely experience?
- The site of damage in the visual pathway is the...
- Bitemporal hemianopsia
- Optic chiasm
A patient has a visual field deficit in the right upper quadrant of her visual field. This is sometimes referred to as “pie in the sky” and is due to a lesion of the...
Optic radiations in the temporal lobe on the left
What lesions are responsible for the following visual field deficits?
A. Monocular blindness - lesion of optic nerve
B. Bitemporal hemianopsia - lesion of optic chiasm
C. Homonymous hemianopsia - lesion of optic tract
D. Upper quadrantopia - lesion of optic radiation in temporal lobe (Meyer's loop)
E. Homonymous hemianopsia + macular sparing - lesion of occipital lobe
- A 35 year-old woman develops a sharp pain in her jaw. The pain is not constant, but rather comes on like an electric shock. Even a slight touch can trigger the pain. The best diagnosis is...
- The best initial treatment for this disorder is...
- Trigeminal neuralgia
Signs and symptoms:
- Brief, severe, shock-like pain usually over V2 and V3
- Usually due to an enlarged blood vessel compressing against the trigeminal nerve near its connection with the pons. Such a compression can injure the nerve's protective myelin sheath and cause erratic and hyperactive functioning of the nerve. This can lead to pain attacks at the slightest stimulation of any area served by the nerve
- Can present in MS, CNS herpes infection, tumors, arachnoid cysts
- Carbamazepine = 1st line
- Can decrease the efficacy of oral contraceptives!
- Other antiepileptics can be used (phenytoin, neurontin), clonazepam
- Surgical decompression may be necessary
Trigeminal nerve anatomy:
- CN V receives sensory input from face + innervates muscles of mastication
- CN V originates in pons → descends to medulla → runs through Meckel's cave → synapses with sensory ganglia in trigeminal ganglion → divides into 3 branches
- V1 = ophthalmic nerve
- V2 = maxillary nerve
- V3 = mandibular nerve
- CN V nucleus descends in brainstem - explains why low brainstem/medullary lesions can cause facial numbness
- CN V also carries afferent limb of corneal reflex - causes eyes to blink if irritated
- CN VII carries efferent limb
A 45 year-old woman wakes up and notices the left side of her mouth is drooping. She fears that she is having a stroke and calls 911. On exam, the left side of her mouth is indeed drooping, she has trouble closing her left eye, and she cannot wrinkle the left side of her face. She tells you as well, that she has some dull pain behind her left ear and that noises sound louder to her on the left side. The remainder of the exam is normal. You tell her presentation is most consistent with...
Facial nerve = CN VII
- Controls muscles of expression
- Lesion of facial nerve nucleus in brainstem or nerve once it exits brainstem produces weakness of entire half of face = Bell's palsy
- Innervates stapedius muscle (ear)
- Patients may have hyperacusis (intolerance to sound)
- Innervates submandibular + sublingual glands
- Receives taste from anterior 2/3 of tongue
- Tx = oral steroids + acyclovir
- Treatment against herpes
Ramsay-Hunt syndrome = herpes zoster infection of CN VII + CN VIII
- Painful rash in ear canal + dysfunction of affected nerves
Types of lesions:
- Lesion of facial nucleus in pons = "peripheral 7th" = Bell's palsy
- Ipsilateral weakness of entire face
- Lesion of cortical motor pathway = "central 7th" = stroke
- Contralateral weakness of lower face
- Upper face gets bilateral cortical representation!
A patient says that she cannot hear when holding the phone near her left ear. You perform the Weber’s test by placing a tuning fork on her forehead and she actually hears the tuning fork louder in her left ear. However when simply holding the tuning fork next to each ear, she hears in better in her right ear. She suffers from...
Conductive hearing loss on the left
Hearing has bilateral representation throughout the CNS - patients cannot become deaf from CNS lesions!
- Damage to primary auditory cortex bilaterally can result in pure word deafness (patient can hear, speak, write, but cannot recognize spoken language)
Conductive vs. sensorineural hearing loss:
- Conductive hearing loss = damage of ossicles
Sensorineural hearing loss = damage to cochlea or vestibulocochlear nerve (CN VIII)
- Presbyacusis = progressive bilateral symmetrical age-related sensorineural hearing loss (common in elderly)
Weber's test = tuning fork placed on forehead
- Conductive hearing loss = sound louder in affected ear
- Sensorineural hearing loss = sound louder in unaffected ear
Rinne's test = tuning fork placed on back of skull then in front of ear
- Conductive hearing loss = bone conduction > air conduction
Sensorineural hearing loss = air conduction > bone conduction
- In normal ear, air conduction > bone conduction
A patient says that she cannot hear when holding the phone near her left ear. She also describes a ringing in that ear and says she “feels like there is something in it.” At times, she becomes so violently dizzy, she feels like she is being thrown to the ground. The most likely diagnosis is...
- Characterized by episodes of unilateral hearing loss, tinnitus, sense of fullness in ear, severe vertigo
- Tx: salt restriction + diuretics
- Rupture of membranous labyrinth, which leads to endolymphatic distention + death of hair cells in cochlea
Benign positional vertigo
- Characterized by episodes of vertigo provoked by changes in head position - usually lying down on affected ear
- Dx: Dix-Hallpike maneuver
- Tx: Epley maneuvers - reposition otolithic material in posterior semicircular canal
- Caused by previous URI
- Characterized by unilateral vestibular dysfunction, associated with nausea, vomiting
- Caused by previous URI
- Characterized by unilateral labyrinth dysfunction, associated with hearing loss/tinnitis
- 3 Semicircular canals detect angular acceleration
- Utricle and saccule = otolithic organs
- Utricle - sensitive to changes in horizontal acceleration
- Saccule - sensitive to changes in vertical acceleration
An evil neurosurgeon wants to lesion someone’s brain to render them unconscious. To do this, he should make a lesion in the...
- A poorly defined area of more than 100 small neural networks throughout the brainstem
- Multiple connections throughout the cortex involved in:
- Motor control
- Sleep and consciousness
- Pain modulation
An elderly alcoholic receives a severe blow to his reticular activating system. He was brought into the ER with a very low lab value which the frantic ER intern fixed in 1 hour. He proudly noted the normalized lab value, but saw that his patient was unconscious. What was low?
Central pontine myelinolysis (CPM)
- Demyelinating disorder that occurs when there is rapid correction of longstanding hyponatremia, causing shifts of free water
- Often in alcoholics, chronically malnourished, medically ill
- Coma, acute quadraparesis, locked-in syndrome
- Poor prognosis
A 75 year-old man has trouble with his gait. On exam, his legs almost seem to cross in front of each other. He has some mild weakness of his hip flexors, and his deep tendon reflexes are quite brisk, with bilateral upgoing toes. This presentation is most consistent with...
- Blue outline = healthy cord
- Red outline = compressed cord from disc herniation
A patient presents saying that he has been dragging his right leg. An MRI reveals an intramedullary lesion on the right side of the spinal cord. What other finding might you find on exam?
Decreased pain and temperature sensation on the left
Decreased proprioception and fine touch on the right
Differences between upper motor neuron and lower motor neuron signs:
Upper motor neuron signs:
- Increased tone, spasticity, reflexes
- Babinski's sign
- Tx: muscle relaxants (Baclofen), botox injection
Lower motor neuron signs:
- Decreased tone, reflexes
- Atrophy, fasciculations
A patient developed pain in his back and numbness in his groin and buttocks after being thrown from a horse. He had no knee reflexes on exam. Where is the lesion?
- Contains 10 nerve fiber pairs (5 lumbar, 5 sacral, and single coccygeal nerve)
- Compression of these nerves, often by herniated disk at L4-L5 or L5-S1, causes cauda equina syndrome
- Numbness in genitals, butt, anus = saddle anesthesia
- Asymmetric lower extremity weakness
- Decreased knee reflexes
- Bowel/bladder retention (often later finding)
- Termination of spinal cord
- Caused by lesion of L1-L2
- Symmetrical lower extremity weakness
- Preserved knee reflexes
- Bowel/bladder incontinence, impotence (often early finding)
A 46 year-old man complains of progressive weakness over the past few months. His symptoms started in his right leg, though now he feels that his left arm is weak too. He also says that his muscles have been “jumping” recently. On exam, he is weak in those areas, a sensory exam is normal, and he has muscle wasting of his intrinsic hand muscles. Reflexes are absent in the right leg, but brisk elsewhere with an upgoing toe on the left. You suspect he has...
Amyotrophic lateral sclerosis
- Symptoms of amyotrophic lateral sclerosis are caused by degeneration of motor neurons of the brain, cranial nerve nuclei, and spinal cord (anterior horn cells)
- Electrophysiologic studies show:
- fasciculations, fibrillations, sharp waves
- Tx: Riluzole
- Prevents stimulation of glutamate receptors
A 66 year-old man presents with gait difficulty for the past two years. On exam, his legs are stiff, he has brisk reflexes, bilateral upgoing toes, and impaired joint position sense. His family says that he has become somewhat paranoid of late. The most likely diagnosis is...
- Causes subacute combined degeneration of spinal cord
- Combined = damage to corticospinal tract + dorsal columns
- Elevated homocysteine + methylmalonic acid (MMA)
- B12 levels may be normal!
- Megaloblastic anemia + hypersegmented neutrophils
- Pernicious anemia, vegetarian diet, post-gastric surgery
- Ntrious oxide
- Interferes with B12 metabolism
- Abnormal signal
- Red = dorsal column
- Blue = lateral corticospinal
- Green = anterior corticospinal
A 56 year-old woman with a history of alcohol abuse is seen in the ER for gait difficulties that have occurred over the past two years. On exam, she has a wide-based gait and cannot stand with her feet together and eyes closed. She is mildly ataxic on finger-nose-finger testing and her strength is intact. An MRI is most likely to show...
Atrophy of the cerebellar vermis
Signs of cerebellar dysfunction:
- Ataxia - incoordination of limbs, posture, gait
- Hypotonia - normal resting muscle tension reduced
- Intention tremor
- Wide-based gait
- Ocular motor abnormalities - saccadic dysmetria, impaired smooth tracking, fixation abnormalities, nystagmus
- Scanning speech - abnormal pauses between words
Causes of cerebellar dysfunction
- Toxins - dilantin, alcohol
- Primary neurodegenerative disorders - olivopontocerebellar atrophy
- paraneoplastic degeneration of cerebellum - GYN cancers
- Spinocerebellar ataxias (SCAs) - genetic disorders
- Vascular disorders
- Cerebellar pathways are "double crossed"
- Lesions to cerebellum present with dysfunction on SAME side of lesion
- MIdline lesions = wide-based gait + imbalance
- Lateral lesions = limb ataxia